Rock Cycle and Soil

Minerals Elements or inorganic compounds that occur naturally and are solid Usually have crystalline structure Almost all of Earth’s crust made of minerals

Rock Cycle Interaction of processes that change rocks from one type to another Recycles material over millions of years Slowest of the earth’s cyclic processes

Three Classifications of Rock Igneous Sedimentary Metamorphic

Igneous Rocks Form from molten rock material (magma) near the surface Underground igneous rocks are called igneous intrusions, granite Magma that reaches the surface & cools is called extrusive igneous rock, basalt or pumice

Sedimentary Rocks Weathered materials that has been deposited in layers and has undergone compaction Make up 75% of earth’s surface, such as limestone, sandstone, bituminous coal

Metamorphic Rocks Preexisting rock that have been altered by high temperature, high pressure, or chemically active fluids For example: graphite, slate, or marble

Soil Terms to Know: Soil Soil Horizons Soil Profile Humus

Soil Structure Four distinct physical parts: Mineral particles Organic matter Water Air Inhabitants include: Plants, animals, fungi, & microorganisms

Soil Horizons Obtained by taking a core sample (soil profile) O horizon Surface-litter layer Rich in organic matter(dead plant material, animal waste, fungi, etc.) A horizon Top-soil layer Porous mixture of humus

Soil Horizons---cont. B horizon Subsoil Zone of illuviation or accumulation (area where minerals leached out of topsoil & surface litter) Typically rich in Fe and Al C horizon Contains weathered pieces of rock Below the extent of most roots & is often saturated with groundwater Lies on top of unweathered bedrock

Soil Texture Determined by the amounts of different sizes and types of mineral particles (clay, silt, & sand) Loams have roughly equal portions of clay, silt, sand, & humus and is best for growing crops. Texture, porosity, permeability determine water- holding capacity, aeration, and workability

Soil Texture—cont. Soil porosity: measure of the spaces per volume of soil & average distances between those spaces. As particle size increases porosity decreases, holds less water and nutrients Soil permeability: rate at which water & air move from upper to lower soil layers As particle size increases permeability increases, infiltration increases

Properties of Soils with Different Textures Soil Texture Nutrient -Holding Capacity Water Infiltra- tion Capacity Water- Holding Capacity AerationWorka- bility ClayGoodPoorGoodPoor SiltMedium SandPoorGoodPoorGood LoamMedium

Soil Acidity and Plant Growth pH of soil influences ability of plants to take in soil nutrients H + bind to negative sites in the soil which allows cation plant nutrients to move through the soil Acid deposition can result in loss of soil fertility

Soil Tests Chemical tests: pH, Salinity, Ion exchange capacity Physical tests: water-holding capacity, percolation rate/permeability, soil texture to determine soil type

SOIL TEXTURAL TRIANGLE

PERCENTAGE OF CLAY Read Numbers on This Side

PERCENTAGE OF SILT

Read Numbers on This Side PERCENTAGE OF SAND

How much clay, silt and sand are in the soils indicated by stars below?

Erosion Movement of soil from one place to another Most is caused by moving water Types of water erosion: Sheet—wide sheet of water moves Rill—water forms small channels Gully—small channels join together & get wider

Water Erosion

Desertification Conversion & loss of marginal semi-arid or arid land to desert Causes: Overgrazing Deforestation with no reforestation Surface mining with no reclamation\ Eroding/salt-concentrating (salinization) irrigation techniques Bad farming practices Soil compaction Poisoning of soils by pesticides/chemicals

Soil Conservation & Regeneration Conservation tillage Residues from previous crops are left in soil Residues cover & help hold soil in place No tillage Leaves the soil undisturbed prior to planting, special machines cut a narrow furrow in the soil for seeds Increases organic material in soils & improve water-holding capacity

Preserving Soil Fertility Two main types of fertilizer: Organic—from natural materials, complex, slow-acting, long-lasting Inorganic—from manufactured chemical compounds Adv: easy to get, soluble, immediately available to plants, increases soil fertility and speeds up growing process Disadv: short-lived, doesn’t provide micronutrients, lacks organic material which decreases water- holding capacity, over-application impacts plants, water, and human health

Organic Fertilizers Animal manure Green manure: fresh or growing vegetation plowed into the soil Compost Spores of mushrooms, puffballs, and truffles: attach to plant roots and help absorb moisture & nutrients

Other Options for improving Soil Adding different soils to adjust water- holding capacity Apply lime for acidic soil Apply sulfur for alkaline soil Burn crop residue to add potassium Plant legumes or apply manure to increase nitrogen Humus: nutrients, water-holding capacity, aeration, helps root growth